This invention relates to an emergency transmitter buoy and a mounting bracket therefor for use on marine vessels
Emergency position indicating radio beacons (EPIRBs) are intended for use by mariners in an emergency situation. According to international agreements, the EPIRB transmits a homing signal on 121.5 mhz only or on both 121.5 and 243 mhz, as well as a satellite beacon signal on 406 mhz. In the event of an accident at sea or other distress situation, the EPIRB is manually deployed or, in the event there is no opportunity for manual deployment, automatically deployed in order to transmit the homing and satellite signals.
The EPIRB transmits a 406.25 mhz identification signal which is received by search and rescue satellite-aided tracking (SARSAT) satellites in orbit around the earth. The SARSAT is able to determine the position coordinates of the EPIRB by doppler shift techniques and to transmit the position of the EPIRB to one of several international ground receiving stations. The ground receiving station relays the position coordinates of the EPIRB as well as identification information relating to the vessel to which the EPIRB is assigned to a Mission Control Center (MCC). The MCC sends the location of the EPIRB to a rescue coordination center which deploys ships, planes, or helicopters as appropriate to the EPIRB site in order to provide rescue operations.
The 121.5 and 243 mhz signals are transmitted to ground based and other rescue facilities. Air and sea search and rescue (SAR) vehicles are able to home-in on the signals and thus locate the EPIRB and those in distress. As the SAR vehicles near the EPIRB, flashing lamp will become visible for final approach.
The EPIRB itself is housed in a buoy which is designed to float on the surface of the water. The upper portion of the buoy includes an antenna cone which contains the transmitting antenna for the buoy; and in order to aid in visual location of the EPIRB buoy in the water, the tip of the antenna cone is provided with a light. The housing of the EPIRB contains a battery pack and transmitter circuitry, and external switching means are provided to manually turn the EPIRB ON or OFF as required. Since the transmission of a signal by the EPIRB immediately sets into motion a full rescue operation, the EPIRB transmitter is never ON unless rescue assistance is required. The EPIRB is also designed to automatically turn ON in an emergency situation when manual activation of the transmitter is not possible.
Because of the high level of effort and cost attendant a rescue operation, especially at sea, the EPIRB transmitter manual and automatic turn-on mechanism must be designed to eliminate as much as possible transmitter false alarms. To this end, various switching schemes for transmitter turn-on have been attempted in the past. For example, since the EPIRB is normally mounted on an outside support surface of the vessel, position sensitive switches have been used which turn the transmitter ON if the orientation of the EPIRB changes drastically. This arrangement can result in false alarms, however, when the EPIRB unit is removed from its mount for inspection or maintenance without first turning the unit fully OFF. The capsizing of a vessel immerses the EPIRB in sea water; and for this reason, switch contacts which close to turn the unit ON when immersed conductive sea water have also been used. However, sea water switches are subject to false alarms caused by the accumulation of salt spray or corrosion which prematurely close the normally open switch contacts and turn the EPIRB transmitter ON.
With regard to the ergonomic design of the EPIRB controls, the transmitter switches must be clearly marked and simple to actuate and should provide visual assurance to an operator or observer that the EPIRB transmitter is in the operating mode which is intended.
The design of the EPIRB buoy mounting bracket is also critical since the bracket must hold and protect the buoy during normal shipboard activities and rough weather but must automatically deploy the buoy in the event of a sudden capsizing. The buoy must be released from the mounting bracket in the event of a capsized or partially submerged vessel; and since the buoy carries a lamp in order to aid in visual location, release from the mounting bracket and proper orientation of the lamp above the surface of the sea is essential. The design of the bracket should also protect the buoy as much as possible from falling objects or from lines or poles which may fall onto and become entangled with the buoy and its support.